A molecularly imprinted polymer (MIP) was synthesized using the herbicide metsulfuron-methyl (MSM) as a template, 2-(trifluoromethyl)acrylic acid as a functional monomer, divinylbenzene as a cross-linker, and dichloromethane as a porogen. This polymer was used as a solid-phase extraction material for the quantitative enrichment of five sulfonylureas (nicosulfuron, thifensulfuron-methyl, metsulfuron-methyl, sulfometuron-methyl, and chlorsulfuron) in natural water and soil samples and off-line coupled to a reversed-phase HPLC/diode array detection (HPLC/DAD). Washing solvent was optimized in terms of kind and volume for removing the matrix constituents nonspecifically adsorbed on the MIP. It has been shown that the nonspecific binding ability of the sulfonylureas to the polymer largely increased along with increasing the concentration of Ca2+ ions in the water sample, whereas complexation of divalent ions with EDTA eliminated this interference completely. The stability of MIP was tested by consecutive percolation of water sample, and it was shown that the performance of the MIP did not vary even after 200 enrichment and desorption cycles. Recoveries of the five sulfonylureas extracted from 1 L of tap water and surface water samples such as river water and rainwater at a 50 ng/L spike level were not lower than 96%. The recoveries of sulfonylureas extracted from 10-g soil sample at the 50 microg/kg level were in the range of 71-139%. Depending on the particular compound, the limit of detection varied from 2 to 14 ng/L in water and from 5 to 12 microg/kg in soil samples. The MIP was also compared with a commercially available C-18 column and an immunoaffinity support with encapsulated polyclonal anti-MSM antibodies in sol-gel glass.

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The development of a direct competitive ELISA for the detection of a broad range of sulfonylurea herbicides (SUs) is described. Polyclonal antibodies were generated in rabbits using three different immunizing haptens. Antiserum with the broadest specificity was obtained with a mesosulfuronbenzylamine derivative which was coupled via a succinic acid spacer to keyhole limpet hemocyanine. A heterologous enzyme tracer which did not contain the succinic acid bridge was prepared using activated horseradish peroxidase. The direct competitive ELISA was optimized and applied for spiked tap and surface water samples. From 30 SUs, 8 compounds showed a molar cross-reactivity (CR) higher than 100% (this value was set for the hapten) and 11 compounds CRs between 10% and 100%. The ELISA can detect 16 SUs at a concentration of 0.1 microg/L or lower. Different surface and tap water samples were spiked with chlorimuron ethyl, metsulfuron methyl, or primisulfuron methyl at concentrations of 100, 200, or 500 ng/L and subsequently analyzed by both ELISA and HPLC-UV. Correlation analysis revealed good agreement between both methods (r2 = 0.983/0.948/0.982; n = 21 for each analyte). Using ELISA, no sample pretreatment other than filtration was necessary.

Immunoaffinity supports (IAS) were prepared using broad specific polyclonal anti-sulfonylurea (SU) antibodies immobilized in sol-gel glass. Two different kinds of supports were applied, crushed sol-gel monoliths and sol-gel-coated highly porous silica particles. Both were used for the quantitative enrichment of SUs in natural water and food samples followed by high-performance liquid chromatography-ultraviolet/diode array detection (HPLC-UV/DAD) and tandem mass spectrometry (LC-MS/MS), respectively. Loading, washing, and elution conditions of IAS were optimized. The capacity of supports was determined for 30 SUs and compared with the cross-reactivity pattern of the direct competitive enzyme-linked immunosorbent assay. The capacities correlated well with the affinity to individual SU compounds. Even analytes to which the polyclonal antibodies showed only a lower cross-reactivity could be enriched to a certain degree, if a sufficient capacity of IAS was provided. The IAS could be reused at least 10 times without a loss of effectiveness. Recovery of 16 selected SUs extracted from spiked water and food samples was dependent on the affinity of both immobilized antibodies to single compounds and matrix interferences. In water, 13 SUs showed recoveries higher than 80% when immunoaffinity extraction was used in combination with LC-UV/DAD. On the basis of the enrichment of 200 mL of aqueous sample, corresponding limit of detection (LOD) values ranged between 20 and 100 ng/L. The recoveries of 10 SUs, which were extracted from 10 g of potato spiked at a 10 microg/kg level, were higher than 75%. For grain samples, recoveries were at the same order for at least five SU herbicides. The LOD of LC-MS/MS measurements was about 1 order of magnitude higher, i.e., gave LODs between 1.1 and 6.9 microg/kg of food sample, depending on the compound and extraction procedure. These LODs provide evidence that the main advantage of the prepared IAS is their high selectivity for group specific recognition of SUs as compared to other nonspecific solid phase extraction materials.

SummaryOchratoxin A (OTA) is a nephrotoxic and nephrocarcinogenic mycotoxin commonly produced by several ubiquitous Aspergillus and Penicillium species. OTA is found predominantly in cereals and derived products, and therefore OTA may be transferred into beer from contaminated grain. Thirty-five samples of German beers were analyzed: OTA was extracted with toluene and purified by solid phase extraction using silica cartridges. OTA was determined by high-performance liquid chromatography with fluorescence detection. Since of fluorescence detection is not specific in this instance, the beer samples were also analyzed by high-performance liquid chromatography electrospray ionization-tandem mass spectrometry (HPLC-ESI-MS/MS). OTA levels in the range of 0.1-0.2 ~g L -1 were found in 9 beer samples, 21 samples contained trace amounts of OTA (< 0.1 ~g L -1) and in 5 samples no OTA was detectable.